The Characteristics And Its Thermal Stability Of The Nanostructurein The Adiabatic Shear Band Of2195Al-Li Alloy

Split Hopkinson pressure bar (SHPB) was used for dynamic loading in hat-shaped specimen made by T6peak aged2195aluminum-lithium alloy to get adiabatic shear band with nanostructure. And corresponding stress-time curve and the stress-strain curve were acquired in this progress. The microstructure of the shear band before and after dynamic loading was investigated by the TEM. The results showed that the adiabatic shear bands hade been formed in the shear zone under the dynamic loading. Equiaxed grains generated at the center of the ASB. whose size is about50～100nm. Precipitates dissolved into the matrix during the dynamic loading progress.The thermal/mechanical parameters during dynamic loading progress were calculated by dynamic loading voltage plus-time curve. The results showed that, during the dynamic loading progress of hat-shaped specimen made by T6peak aged2195aluminum-lithium alloy, the average strain rate was1.69×105/s in96μs, true stress peak value was720MPa, and adiabatic temperature rise was833K, higher than the lowest recrystallization temperature of2195Al-Li alloy, which certificated the recrystallization and precipitates dissolving in the ASB Thermodynamically. during the dynamic loading progress, grain size decreased from micro-scale into nano-scale by RDR mechanism. The heat transfer was also considered in the progress by Fourier heat transfer equation, the effect of Static recrystallization was limited and can be ignored during the progress of stretched sub-grain and nano-axis crystal.EBSD was used to investigate the evolve of microstructure of ASB after annealling at373K-673K, the results showed that after annealling at different temperature, the grain size increasing with the elevating temperature, after annealling at373K-673K there’s no notable growth happened on the grains in the ASB, and after annealling at573K,the grains grew to0.22μm at a high speed. the size of grains evolved to1.77μm after annealling at673K for1h.The results of hardness shows that, the mechanical properties of this material decreased significantly at673K, the critical temperature of the nano-grain growing sharply is673K, the nanostructure stayed stable below673K.